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Orientation of nocturnally migrating Swainson's thrush at dawn and dusk: Importance of energetic condition and geomagnetic cues

Sandberg, Roland LU ; Moore, FR; Bäckman, Johan LU and Lohmus, M (2002) In The Auk 119(1). p.201-209
Abstract
We studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds chose directions in accordance with migration across the Gulf of Mexico, whereas lean birds oriented away from the coast, possibly in search of habitats suitable for refuelling. Whereas the orientation of fat Swainson's Thrushes was affected by experimental shifts of the magnetic field, the response during morning tests was larger than expected.... (More)
We studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds chose directions in accordance with migration across the Gulf of Mexico, whereas lean birds oriented away from the coast, possibly in search of habitats suitable for refuelling. Whereas the orientation of fat Swainson's Thrushes was affected by experimental shifts of the magnetic field, the response during morning tests was larger than expected. A parallel series of orientation cage experiments performed during evening twilight showed a response to deflected magnetic fields that was close to the expected shift, which suggests a difference in integration of directional information between early morning and evening twilight activity. However, within-individual response to deflected magnetic fields was of the same magnitude during both morning and evening tests. (Less)
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author
organization
publishing date
type
Contribution to journal
publication status
published
subject
in
The Auk
volume
119
issue
1
pages
201 - 209
publisher
BioOne
external identifiers
  • wos:000174275200017
ISSN
0004-8038
language
English
LU publication?
yes
id
6c54e7cf-9489-43d0-b54a-c94bbef58435 (old id 145633)
alternative location
http://www.bioone.org/bioone/?request=get-document&issn=0004-8038&volume=119&issue=01&page=0201
date added to LUP
2007-06-25 11:02:28
date last changed
2016-04-16 04:54:56
@article{6c54e7cf-9489-43d0-b54a-c94bbef58435,
  abstract     = {We studied the early morning cage orientation of nocturnally migrating Swainson's Thrushes (Catharus ustulatus) during three fall migration seasons. The results were compared with earlier free-flight release tests under starry skies and were found to be consistent with continuation of migratory flights in the expected seasonally appropriate direction. Energetic condition proved decisive: fat birds chose directions in accordance with migration across the Gulf of Mexico, whereas lean birds oriented away from the coast, possibly in search of habitats suitable for refuelling. Whereas the orientation of fat Swainson's Thrushes was affected by experimental shifts of the magnetic field, the response during morning tests was larger than expected. A parallel series of orientation cage experiments performed during evening twilight showed a response to deflected magnetic fields that was close to the expected shift, which suggests a difference in integration of directional information between early morning and evening twilight activity. However, within-individual response to deflected magnetic fields was of the same magnitude during both morning and evening tests.},
  author       = {Sandberg, Roland and Moore, FR and Bäckman, Johan and Lohmus, M},
  issn         = {0004-8038},
  language     = {eng},
  number       = {1},
  pages        = {201--209},
  publisher    = {BioOne},
  series       = {The Auk},
  title        = {Orientation of nocturnally migrating Swainson's thrush at dawn and dusk: Importance of energetic condition and geomagnetic cues},
  volume       = {119},
  year         = {2002},
}